DESCRIPTION: The goal of this research program is to develop and characterize novel small molecule inhibitors of latent Kaposi's Sarcoma Associated Herpesvirus (KSHV) infection. KSHV/Human Herpes Virus 8 (HHV-8) is a human herpesvirus and the causative agent of Kaposi's sarcoma's (KS). KS is a lymphatic-endothelial cell malignancy that occurs most frequently and severely in patients with HIV-AIDS. KS affects about 20% of HIV- positive patients who are not taking anti-HIV drugs. In addition, there appears to be an increase of new cases of KS in patients whose HIV is under control. KSHV has also been implicated in several lymphoid disorders, including pleural effusion lymphoma and Castleman's disease. At present, there are no KSHV-specific therapies that effectively block KSHV infection or latency, and therefore it remains impossible to effectively treat or prevent KSHV-related pathologies. Latent infection and viral pathogenesis require one viral encoded protein, Latency-Associated Nuclear Antigen (LANA), which functions in the replication and maintenance of the viral genome during latency, and alters cellular gene expression programs that promote virus and host cell survival. Genetic and biological disruption of LANA, including siRNA depletion and gene deletion, block viral genome persistence during latent infection. The LANA DNA binding domain (DBD) has been characterized biochemically and structurally, and serves as an ideal target for small molecule inhibition of KSHV infection. The development of a safe and effective inhibitor of LANA would provide an important therapeutic strategy for the treatment of KSHV-associated malignancies. This program builds on the successful completion of a high- throughput screen for small molecule inhibitors of LANA, and on our recent determination of the X-ray crystal structure of the LANA DNA binding domain. The risk of this project is further mitigated by our experience developing small molecule inhibitors targeting Epstein-Barr Virus protein EBNA1 with similar structure and function as LANA. We have used high-throughput screening, crystallography, and structure-based drug design approaches to optimize validated hits into lead compounds that possess mid to low-nanomolar activity for EBNA1. In this R01 proposal, we plan to apply a similar strategy to identify and optimize LANA inhibitors for the treatment of KSHV-related disease.